1. Field of the Invention
The invention is directed to a laser scanning microscope and to a control method for a laser scanning microscope of this kind.
2. Description of Related Art
In order to obtain sharp imaging of the sample in a laser scanning microscope, the distance between the microscope objective and the sample is usually varied to adjust the focus position. To this end, either the sample stage with the sample or the microscope objective can be moved. It is also possible to combine the two movements.
However, the relative movements between the objective and the sample are problematic under some circumstances. For example, in electrophysiological experiments, a large number of delicate contacts are connected to the sample. A movement of the sample stage could cause these contacts to be torn out and, for this reason, is generally ruled out for fixing the focus position. Aside from this, movement of the objective may also be ruled out, for example, when contacts are guided past close to the objective or when the objective is immersed in a specimen liquid.
So-called internal focusing of objectives is known in microscopes in the prior art. For example, DE 10 2005 034 441 A1 shows a microscope objective with an adjusting device by means of which an optical element inside the objective is displaceable along the optical axis in such a way that the focus position is displaced in direction of the optical axis relative to the front element of the objective.
Sharp imaging can be achieved without relative movement of the objective and sample by means of internal focusing of the objective. However, the required special objective is extremely costly.